Various kinds of such power-assisted on/off valves are known in the art, and have been made practically viable. However, such power-assisted on/off valves were large, required extremely high-precision machining of the parts thereof, and it was difficult to obtain a stable performance in use over a long period of time.
Japanese Patent No. 3,392,301 discloses one embodiment of a power assisted on/off valve in the prior art.